Method for generating multimedia data associated with a system for practicing sports

ABSTRACT

Motion sickness is reduced for users of mechanical systems used to practice sports that comprise an immersive virtual reality device. In particular, the use of prediction and interpolation algorithms enable fluid movements to be displayed within the virtual environment.

The present invention relates to the area of mechanical systems forpracticing sports comprising an immersion device in virtual reality andmore particularly methods making it possible to reduce motion sicknesswhen using such a system.

Mechanical systems for practicing sports are systems allowing a user topractice a sporting activity indoors by generally simulating a realsporting activity on a controlled apparatus. It is possible to citeindoor bikes, cross-trainers, indoor rowing machines, treadmills and soon as examples of such systems. These systems are typically made up ofthe sports apparatus in itself which allows the user to make an effort.This is typically a bicycle, a rowing machine etc. This sports apparatusis coupled with an adjustable resistance which makes it possible tocontrol the effort level which has to be provided by the user when usingthe sports apparatus. This resistance may assume a variety of forms, itmay be, for example, a flywheel slowed down by friction or by anadjustable magnetic field or even oars immersed in water, the movementof which slows down the movement of the sports apparatus as is the casein certain indoor rowing machines.

Nowadays, the adjustment of the resistance is generally controlled by acomputer controlling the activity. This control computer allows thedisplay of different activity programs and the display of ahuman-machine interface making it possible to choose one's program andthus to act on the level of resistance. The functions of the controlcomputer are complemented by functions for monitoring and establishingstatistics on the activity sessions, monitoring the user's heart rateetc.

Virtual reality is a visual or auditive, immersive, interactive,computer-based simulation of real or imaginary environments. The purposeof virtual reality is to provide someone (or several people) with asensory-motor and cognitive activity in an artificial world, createddigitally, which may be imaginary, symbolic or a simulation of certainaspects of the real world.

Coupled with a mechanical system for practicing sports, virtual realitymakes it possible to simulate the sporting activity in a virtualenvironment which can, for example, simulate an outdoor activity. Thus,the activity is made more entertaining and enjoyable than an activity ina fixed indoor environment.

Despite numerous possible applications, the use of virtual reality isnot yet widespread and attempts to market a product based on virtualreality have been hampered by a recurring problem: motion sickness orcybersickness.

Motion sickness or cybersickness occurs when being exposed to a virtualenvironment brings about symptoms which are similar to the symptoms oftravel sickness. This syndrome causes dizziness, headaches, feelings ofdisorientation, nausea etc. It can occur during the virtual experience,but equally when returning to reality and may last for several hours.

Motion sickness is different from travel sickness in that it can becaused by the visual perception of movements without an actual movementof the user being necessary. Motion sickness is the critical pointlimiting the launch of commercial applications based on virtual reality.

The aim of the present invention is to address the aforementioneddrawbacks and more particularly to reduce motion sickness in the user ofa mechanical system for practicing sports comprising an immersion devicein virtual reality. The invention is based on the use of prediction andinterpolation algorithms allowing the display of a fluid movement withinthe virtual environment.

The invention relates to a method for generating multimedia data by avirtual environment generator associated with a mechanical system forpracticing sports and for a virtual reality headset characterized inthat it comprises:

-   -   a step of receiving kinetic samples at a first regular or        irregular frequency, these kinetic samples being representative        of a position of the user in a movement estimated to come from        the use of the mechanical system for practicing sports during an        exercise session;    -   a step of determining a camera position within a virtual        environment, said position representing the position of said        user in the virtual environment, said determination being        carried out at a second regular frequency, called display        frequency, higher than the first frequency and by interpolating        the received position of the user;    -   a step of generating multimedia data corresponding to the camera        position at the display frequency.

According to a particular embodiment, the step of determining the cameraposition comprises:

-   -   a step of calculating at the first frequency an instantaneous        speed corresponding to the speed of the user between the last        received sample and the previous one.

According to a particular embodiment, the method further comprises:

-   -   a step of determining an instantaneous speed adjusted from the        instantaneous speed, of the simulated position of the user in        the virtual environment and of the position received in the last        sample, this step being carried out at the first frequency.

According to a particular embodiment, the method further comprises:

-   -   a step of determining the camera position at the display        frequency as a function of the previous camera position and of        the adjusted instantaneous speed.

According to a particular embodiment, the method further comprises:

-   -   a step of determining the end of the movement when an elapsed        period of time without receiving a new kinetic sample is greater        than a threshold depending on the average temporal interval        between two kinetic samples.

According to a particular embodiment, the method further comprises:

-   -   a step of transcribing the body movements made by the user to        the camera movements in the virtual environment.

According to a particular embodiment, the mechanical system forpracticing sports being an indoor rowing machine, the method furthercomprises:

-   -   a step of reversing the direction of movement.

The invention also relates to a system for practicing sports comprising:

-   -   a mechanical system for practicing sports;    -   a virtual environment generator associated with the mechanical        system for practicing sports; and    -   a virtual reality headset connected to the virtual environment        generator;        characterized in that the virtual environment generator        comprises:    -   means of receiving kinetic samples at a first regular or        irregular frequency, these kinetic samples being representative        of a position of the user in a movement estimated to come from        the use of the mechanical system for practicing sports during an        exercise session;    -   means of determining a camera position within a virtual        environment, said position representing the position of said        user in the virtual environment, said determination being        carried out at a second regular frequency, called display        frequency, higher than the first frequency and by interpolating        the received position of the user;    -   means of generating multimedia data corresponding to the camera        position at the display frequency.

According to a particular embodiment, the virtual reality headset has anOLED display.

According to a particular embodiment, the virtual reality headset has afield of vision of less than 180 degrees.

According to a particular embodiment, the system comprises a hardwareadjustment for adjusting the interpupillary distance.

The invention also relates to a computer program comprising instructionsadapted to the implementation of each of the method steps according tothe invention when said program is executed on a computer.

The invention also relates to a means of storing information, eitherremovable or non-removable, partially or completely readable by acomputer or a microprocessor comprising code instructions of a computerprogram for executing each of the method steps according to theinvention.

In a particular embodiment, steps of the abovementioned method aredetermined by computer program instructions.

Consequently, the invention also relates to a computer program on astorage medium, this program being capable of being implemented by amicroprocessor, this program comprising instructions adapted to theimplementation of the method steps as mentioned above.

This program may use any programming language and be in the form ofsource code, object code, intermediate code between source code andobject code, such as in a partially compiled form, or in any otherdesirable form.

The invention also relates to a storage medium readable by amicroprocessor, and comprising instructions of a computer program asmentioned above.

The storage medium may be any entity or device capable of storing theprogram. For example, the medium may comprise a storage means, such as aROM, for example a ROM chip, or else a magnetic recording medium, forexample a hard drive, or else a flash memory.

Furthermore, the storage medium may be a transmitted medium such as anelectrical or optical signal which may be sent via an electric oroptical cable, by radio or by other means. The program according to theinvention may be in particular downloaded on a storage platform of anetwork such as the Internet.

Alternatively, the storage medium may be an integrated circuit in whichthe program is incorporated, the circuit being adapted to execute or tobe used in the execution of the method in question.

The abovementioned storage medium and computer program have features andadvantages similar to the method which they implement.

Other features and advantages of the invention will become apparent inthe description hereinafter in relation to the appended drawings, givenby way of non-limiting examples:

FIG. 1 shows an example of a system for practicing sports according tothe invention;

FIG. 2 shows the functional relationships between the differentcomponents of the system according to one exemplary embodiment of theinvention;

FIG. 3 shows the method for generating multimedia data in one exemplaryembodiment of the invention;

FIG. 4 shows the interpolation method according to one exemplaryembodiment of the invention;

FIG. 5 is a schematic block diagram of a device for processinginformation for the implementation of one or several embodiments of theinvention.

Motion sickness is triggered in users of virtual reality for severaldifferent reasons, some of them technical, others due to the way thehuman body functions. Among the predominant causes which induce\ motionsickness when using immersive virtual reality, we can name the followcauses:

The functional mismatch between the visual experience and the motoractivity. This first cause is one of the main ones and occurs when thevirtual environment does not react coherently with the actual movementsof the user of the mechanical system for practicing sports. This occurs,for example, when there is an excessive delay between a movement of theuser and the display of the consequence of this movement in the virtualenvironment.

Another cause of motion sickness is an effect of blurring or jerkinesswhich brings about a discrepancy between the virtual experience and thevision in the real world.

Motion sickness also occurs when the virtual image displayed does notrespect the human eye's field of vision. The use of wider or narrowerviewing angles triggers a mismatch in the brain.

Postural instability during the virtual reality experience may occurwhen the position of the body which naturally tends to readjust itsposition to align itself upright is inconsistent with the virtualenvironment. In this case, there is an inconsistency between theperceived visual information and the information of the user's innerear. This postural instability triggers motion sickness.

People have a variable interpupillary distance of around 62 mm. Thisdistance may vary slightly from person to person. The result of thisvariation is a blurry sensation with respect to the perceived image anda rejection of the virtual experience by the user, causing motionsickness.

Finally, when the transition between the virtual world and the realworld is too quick, users complain of experiencing nausea and dizziness,which are typical of motion sickness.

FIG. 1 shows an example of a system for practicing sports according tothe invention. A user 1.1 uses an indoor rowing machine 1.2. This rowingmachine 1.2 comprises a kinetic actuator 1.3 which allows them toinstigate a movement typically by pulling on the actuator connected by astrap to a kinetic sensor. 1.4. The sensor offers resistance to themovement, said resistance being controlled by a control computer 1.5.This control computer in addition to the control of the device'sresistance records the parameters of the movement, tensile force, numberof strokes per minute, extent of pulling and other information conveyedby the kinetic sensor 1.4. Based on these parameters, it calculatesstatistical information aimed at the user and displays it on the controlscreen incorporated in the control computer 1.5. As part of theinvention, the mechanical system for practicing sports also comprises avirtual environment generator 1.6. Given that the user is provided witha viewing headset 1.7, the virtual environment generator 1.6 obtains arange of parameters on the movement generated by the action of the userfrom the control computer 1.5. For example, it is possible to regularlyobtain the position of the user as well as the time elapsed since thebeginning of the session. A session is defined as the period of timebetween the user starting to use the system and stopping. These movementparameters may be obtained either upon request from the virtualenvironment generator or issued more or less regularly by the controlcomputer according to the models of the mechanical systems forpracticing sports.

The control computer and the virtual environment generator are twodevices for processing information which are programmed specifically forthe function to be carried out. They are typically devices such as theone shown in FIG. 5 and described below. The person skilled in the artlikewise understands that in certain embodiments, the functions of thecontrol computer and virtual environment generator may be carried out byone and the same device for processing information without modifyingtheir operating mode.

This is just one example; an exercise bicycle, a cross-trainer or atreadmill could be used in the same way.

FIG. 2 shows the functional relationships between the differentcomponents of the system according to one exemplary embodiment of theinvention.

The kinetic actuator 1.3 allows the user to instigate the movement onthe mechanical system for practicing sports. This movement istransmitted, arrow 2.1, to the inertial sensor 1.4. This transmission istypically mechanical, for example via a pull strap in the case of arowing machine. It may be a drive chain pedal unit in the case of anexercise bicycle.

The inertial sensor 1.4 captures mechanical movement and transforms itinto a digital datum of movement which is transmitted, arrow 2.2, to thecontrol computer 1.5. The transmission may assume any form known by theperson skilled in the art, wired or wireless, allowing the transmissionof a digital signal between the sensor and the control computer 1.5, forexample a serial bus, a simple cable transmitting modulated digitalinformation or a Bluetooth link etc.

The control computer 1.5 therefore uses this movement information tocarry out, inter alia, an assessment of movement. This assessment ofmovement uses the movement as well as a model making it possible toassess the movement that a real boat experiencing the same effort from arower would have. The way in which this assessment is carried out is notthe subject of this document and will not be described further here.This assessment allows the control computer 1.5 to transmit thisinformation, arrow 2.3 to the virtual environment generator 1.6. Thistransmission may be periodic according to the control computer's ownfrequency or generated by an event. For example, certain exercisebicycles transmit the movement information with each turn of the wheelby the user. It is understood in this situation that the transmission isirregular and unpredictable. In still other cases, the transmission maybe carried out upon request of the virtual environment generator. Inthis case, the latter is in charge of the transmission frequency withinthe limits of the control computer's capabilities. The control computergenerally imposes a maximum frequency which cannot be exceeded. Heretoo, the transmission may be carried out by any means. It may be a wiredtransmission, for example USB, Ethernet or serial connection. It may bea wireless transmission, for example Bluetooth or Wifi. It may also beany means of inter-process communication when the two functions of thecontrol computer and virtual environment generator are carried out bythe same device for processing information.

Typically, the virtual reality headset 1.7 also transmits movementinformation to the virtual environment generator 1.6. This informationrelates to the head movements made by the user and is integrated intothe movement information received by the control computer 1.5 for thegeneration of the virtual environment.

Other sensors may be used to retrieve various information on the user'smovements and/or their environment:

-   -   sensors installed on the user: accelerometer, magnetometer,        gyroscope, sensors of physiological features (for example, heart        rate, respiratory rate, body temperature, blood pressure, oxygen        saturation etc.)    -   distant sensors such as the camera (whatever the spectrum),        sonar, electromagnetic sensors etc.

Using this movement information, the virtual environment generator 1.6updates the position of the user in the environment. This essentiallyinvolves locating the camera in a three-dimensional environment. Then,with the position of the camera having been determined, the imagesviewed by this camera are generated to be sent back to the virtualreality headset 1.7 with the sound accompanying the scene. The virtualreality headset is typically a three-dimensional viewing headsetequipped with headphones. The images generated are therefore typicallythree-dimensional images comprising an image intended for each of theuser's eyes.

The transmission 2.4 between the headset and the virtual environmentgenerator may be carried out by any means. It may be a wiredtransmission, for example USB, Ethernet or serial connection. It may bea wireless transmission, for example Bluetooth or Wifi.

FIG. 3 shows the method for generating multimedia data in an exemplaryembodiment of the invention. These data are generated for the virtualreality headset based on the movement data transmitted by the controlcomputer.

The kinetic samples 3.1 are made up of the data transmitted by thecontrol computer. A sample corresponds to a transmission of data. Thespecific contents of the data transmitted may vary between the differentmechanical systems for practicing sports. In any case, these data arerepresentative of a position of the user in a movement estimated to comefrom the use of the mechanical system for practicing sports during anexercise session. In the exemplary embodiment based on an indoor rowingmachine, the data transmitted comprise a distance traveled and anassociated timestamp which gives the date relative to the start of thesession when this distance was traveled virtually by the user using themechanical system for practicing sports.

The accumulation step 3.2 allows the virtual environment generator tostore the received samples. These samples are transmitted according to atemporal frequency which may or may not be regular. The accumulationmakes it possible to store these samples when they arrive for theirsubsequent use.

The kinetic interpolation step 3.3 makes it possible to carry out aninterpolation between the samples in order to generate a sufficientfrequency of samples to obtain a fluid simulation of the movement in thevirtual environment. The details of this interpolation will be describedlater on in relation to FIG. 4. In fact, the transmission frequency ofthe samples is typically inadequate and without interpolation would leadto a jerky movement of the camera in the virtual environment.

Step 3.4 determines the movement of the camera in the virtualenvironment as a function of the interpolated samples. The cameraposition represents the position of the user in the virtual environmentcorresponding to their activity on the mechanical system for practicingsports. The movement of the camera also incorporates the head movementdata transmitted by the headset and/or the body movement datatransmitted by other position sensors. This aspect is not developed inthe present document but is essential for preserving the coherencebetween the actual movements of the user and the virtual movements.

Step 3.5 therefore consists in generating the images and possibly thesound corresponding to the new camera position in the virtualenvironment. These images and the sound represent the virtualenvironment such as it is viewed by the camera. These data constitutethe multimedia data 3.6 that will be transmitted to the user in order tobe reproduced by the headset, thus immersing the user in the virtualworld.

FIG. 4 shows the interpolation method according to an exemplaryembodiment of the invention.

One of the main causes of motion sickness is the lack of fluidity ofcamera movements in the virtual environment. If the image is jerky, theperceived movement is no longer consistent with the movements of theuser and confuses their inner ear. Yet, the samples transmitted by thecontrol computer of the mechanical system for practicing sports aretransmitted with a frequency which is generally not high, typically inthe order of 50 Hz for a rowing machine or even between 0.5 Hz and 2 Hzfor a bicycle transmitting a sample upon each turn of the pedal.Experience shows that an image refresh carried out by the virtualreality headset greater than or equal to 60 Hz is desirable in order toreduce the risk of motion sickness. In the exemplary embodiment, therefresh frequency is 75 Hz. In order to obtain fluid movements at thedisplay refresh frequency, it is therefore necessary to proceed with aninterpolation of the camera positions and to not simply update thisposition when a new sample is transmitted.

The interpolation method accepts the movement data 4.1 transmitted bythe control computer. These data comprise in the exemplary embodiment acurrent distance and the timestamp of the current time.

The interpolation method can be broken down into two distinct moduleswhich are not carried out at the same frequency. A first module,symbolized by the arrow 4.8 is carried out at the transmission frequencyof the samples, this transmission frequency possibly being irregular andunpredictable. It consists in calculating an adjusted instantaneousspeed 4.5. Next, a second module symbolized by the arrow 4.9 uses thisadjusted instantaneous speed to produce a camera position 4.7 at thedisplay frequency, which is 75 Hz in the exemplary embodiment.

When a sample is received, a step 4.2 makes it possible to calculate theinstantaneous speed based on the movement data of the received sampleand the movement data of the previous sample. The instantaneous speedcorresponds to the speed of the user between the last received sampleand the previous one. First of all, the difference of the distancestraveled between the two samples is calculated,delta_distance=current_distance−previous_distance. The time differenceseparating the two sample is then calculated,delta_time=current_time−previous_time. The instantaneous speed 4.3therefore corresponds to the ratio of the two,instantaneous_speed=delta_distance/delta_time.

The instantaneous speed is used to update the position of the user atthe display frequency whilst waiting for a new sample to be received.When it arrives, it is probable that the simulated position of the userin the virtual environment is late or early compared with the positionreceived in the last sample. In order to avoid the accumulation of theseestimation errors, it is appropriate to adjust the movement speedestimated when a new sample is received, that is to say to reduce it ifthe estimation is early or to increase it if the estimation is late. Theadjustment step 4.4 makes it possible to calculate an adjustedinstantaneous speed 4.5. This adjustment prevents the positioncalculated in the virtual environment from deviating with respect to theposition transmitted by the samples without causing jerkiness as asudden recalibration would when receiving the sample. Typically, theadjustment consists in applying an adjustment coefficient to theinstantaneous speed as a function of the deviation between the newreceived sample and the estimated position. This adjustment coefficientis less than 1 when the new sample is early and more than 1 when the newsample is late. In the exemplary embodiment, the adjustment coefficientis comprised between the values 0.8 and 1.2. The adjustment coefficientassumes the maximum values 0.8 or 1.2 when the deviation between thereceived sample and the estimated position is greater than 1 meter. Itprogresses in a linear fashion between the two limits as a function ofthe deviation for deviations less than or equal to 1 meter. Of course,these numerical values constitute an example within the context of arowing machine and could be different depending on the type of systemfor practicing sports considered and the frequency of the samples.

It is therefore this instantaneous speed 4.5 which is used by step 4.6to determine the current camera position at the display frequency in thevirtual environment. The camera position is then updated at the refreshfrequency according to the following formula:position=previous_position+adjusted*dt instantaneous speed, in which dtstands for the time between two refreshes, i.e. 13.3 ms for a frequencyof 75 Hz.

Certain mechanical systems for practicing sports only transmit sampleswhen the user is moving, for example a bicycle which transmits a sampleupon each turn of the peddle. For these systems, only the detection ofnot receiving a sample makes it possible to detect that the user hasstopped. Advantageously, a step of determining the stop is thereforeadded to this method. For example, the stop is determined when anelapsed period of time without receiving a new kinetic sample is greaterthan a threshold depending on the average temporal interval between twokinetic samples. For example, the threshold may be defined ascorresponding to three times the average temporal interval between twokinetic samples.

Thus, a fluid movement at the sufficient display frequency is generatedwhich allows the risk of triggering motion sickness in the user to bereduced. This risk is further reduced by the use of a headset using anOLED screen having a low persistence of vision although any otherdisplay technology may be used.

Advantageously, the headset used has a field of vision of less than 180degrees, thus respecting the fields of vision to which the brain isaccustomed, which likewise reduces the risk of motion sicknessoccurring.

Postural instability during the virtual reality experience iscounteracted by transcribing the body movements made by the user to thecamera movements in the virtual environment. Thus, the visualinformation and that of the inner ear are matching at all times.

Advantageously, the system is provided with a hardware adjustment, forexample at the level of the headset, for adjusting the interpupillarydistance and thus perfectly adapting the three-dimensional experience tothe user's morphology.

In order to ease the transitions between the real world and the virtualworld, the system has transition spaces. This area enables the user toget used to the virtual experience and to carry out their preliminaryadjustments before launching the simulation.

In the case of an indoor rowing machine, logic dictates that the userhas their back to the direction of travel of the boat which they operatein the virtual environment. It turns out that this way of advancing inthe virtual environment is not comfortable and may contribute to theoccurrence of motion sickness. Reversing the direction of travel of thevirtual boat and thus advancing with the user facing the direction ofmovement does not cause any discomfort for the user and actually reducesthe risk of motion sickness occurring. Advantageously, the virtualenvironment generator therefore incorporates a reversal of the directionof movement in the case of an indoor rowing machine.

FIG. 5 is a schematic block diagram of a device for processinginformation 500 for the implementation of one or several embodiments ofthe invention. The device 500 for processing information may be aperipheral device such as a microcomputer, a workstation or a mobiletelecommunication terminal. The device 500 comprises a communication busconnected to:

-   -   a central processing unit 501, such as a microprocessor, called        CPU;    -   a random-access memory 502, called RAM, to store the executable        code of the method of performing the invention as well as the        registers adapted to record variables and parameters which are        necessary for the implementation of the method according to        embodiments of the invention; its storage capacity may be        complemented by an optional RAM memory connected to an extension        port, for example;    -   a read-only memory 503, called ROM, to store IT programs for the        implementation of the embodiments of the invention;    -   a network interface 504 is normally connected to a communication        network on which digital data to be processed are transmitted or        received. The network interface 504 may be a single network        interface or composed of a set of different network interfaces        (for example wired and wireless, interfaces or different types        of wired or wireless interfaces). Data packets are sent on the        network interface for the transmission or are read from the        network interface for being received under the control of the        software application executed in the processor 501;    -   a user interface 505 for receiving inputs of a user or for        displaying information to a user;    -   an optional storage medium 506 called HD;    -   an input/output module 507 for receiving/sending data from/to        external peripheral devices such as hard drive, removable        storage medium or others.

The executable code may be stored in a read-only memory 503, on thestorage medium 506 or on a digital removable medium such as a disk, forexample. According to one version, the executable code of the programsmay be received by means of a communication network, via the networkinterface 504, in order to be stored in one of the storage means of thecommunication device 500, such as the storage medium 506 before beingexecuted.

The central processing unit 501 is adapted to control and direct theexecution of the instructions or the portions of software code of theprogram or programs according to one of the embodiments of theinvention, instructions which are stored in one of the aforementionedstorage means. After being powered up, the CPU 501 is capable ofexecuting instructions stored in the main RAM memory 502, relative to asoftware application, after these instructions have been loaded from theROM for example. Such a software, when it is executed by the processor501, triggers the steps in the flow charts illustrated in figures X to Yin order to be executed.

In this embodiment, the device is a programmable device which uses asoftware to implement the invention. However, in the alternative, thepresent invention may be implemented in hardware (for example, in theform of an application-specific integrated circuit or ASIC).

Of course, in order to meet specific needs, a skilled person in thefield of the invention will be able to apply modifications in thepreceding description.

Although the present invention has been described above in reference tospecific embodiments, the present invention is not limited to thespecific embodiments, and the modifications which are in the scope ofapplication of the present invention will be obvious for a personskilled in the art.

1-13. (canceled)
 14. A method for generating multimedia data by avirtual environment generator associated with a mechanical system forpracticing sports and for a virtual reality headset, the methodcomprising: receiving kinetic samples at a first regular or irregularfrequency, the kinetic samples being representative of a position of auser in a movement estimated to come from use of the mechanical systemfor practicing sports during an exercise session; determining a cameraposition within a virtual environment, the position representing theuser's position in the virtual environment, the determination beingcarried out at a display frequency and by interpolating the receivedposition of the user, the display frequency being a second regularfrequency higher than the first frequency; generating multimedia datacorresponding to the camera position at the display frequency.
 15. Themethod of claim 14, wherein determining the camera position comprisescalculating at the first frequency an instantaneous speed correspondingto the user's speed between the last received sample and the previousreceived sample.
 16. The method of claim 15, wherein the method furthercomprises: determining an adjusted instantaneous speed from theinstantaneous speed of the simulated position of the user in the virtualenvironment and the position received in the last sample, wherein theadjusted instantaneous speed determine is carried out at the firstfrequency.
 17. The method of claim 16, wherein the method furthercomprises: determining the camera position at the display frequency as afunction of the previous camera position and of the adjustedinstantaneous speed.
 18. The method of claim 14, wherein the methodfurther comprises: determining that movement has stopped when an elapsedperiod of time without receiving a new kinetic sample is greater than athreshold depending on the average temporal interval between two kineticsamples.
 19. The method of claim 14, wherein the method furthercomprises: transcribing body movements made by the user to the cameramovements in the virtual environment.
 20. The method of claim 14,wherein the mechanical system for practicing sports is an indoor rowingmachine and the method further comprises reversing a direction ofmovement.
 21. A system for practicing sports, the system comprising: amechanical system for practicing sports; a virtual environment generatorassociated with the mechanical system for practicing sports; and avirtual reality headset connected to the virtual environment generator,wherein the virtual environment generator comprises: means of receivingkinetic samples at a first regular or irregular frequency, the kineticsamples being representative of a position of the user in a movementestimated to come from the use of the mechanical system for practicingsports during an exercise session; means of determining a cameraposition within a virtual environment, the camera position representingthe user's position in the virtual environment, the determination beingcarried out at a display frequency and by interpolating the receivedposition of the user, the display frequency being a second regularfrequency higher than the first frequency; means of generatingmultimedia data corresponding to the camera position at the displayfrequency.
 22. The system of claim 21, wherein the virtual realityheadset has an OLED display.
 23. The system of claim 21, wherein thevirtual reality headset has a field of vision of less than 180 degrees.24. The system of claim 21, wherein the system comprises a hardwareadjustment for adjusting interpupillary distance.
 25. A computer programcomprising instructions adapted to implement each of the method steps ofclaim 14, wherein the program is executed on a computer.
 26. Means ofstoring information, either removable or non-removable, partially orcompletely readable by a computer or a microprocessor comprising codeinstructions of a computer program for executing each of the methodsteps of claim 14.